Multicolor tunable bright photoluminescence in Ca 2+ /Mg 2+ modified Eu 3+ doped ZnGa 2 O 4 phosphors under UV excitation for solid state lighting applications.

The Eu ³⁺ doped and Mg ²⁺ /Ca ²⁺ co-doped ZnGa ₂ O ₄ phosphor samples were synthesized by solid-state reaction method and their structural and optical properties studied. The phase, crystallinity and particles size of the phosphor samples were studied by XRD and SEM measurements. EDS analyses were used to identify the elements present in the phosphor materials. The vibrational groups present in the phosphor samples were examined by Fourier transform infrared (FTIR) measurements. Pure ZnGa ₂ O ₄ emits intense blue light under 260 nm excitation. However, Eu ³⁺ doped and Mg ²⁺ /Ca ²⁺ co-doped ZnGa ₂ O ₄ phosphor samples exhibit intense red emission under 393 nm excitation. A bluish white color is observed in these samples under 290 nm excitation. The maximum PL emission intensity is found at 0.1 mol% Eu ³⁺ doping concentration. For higher concentrations, concentration quenching was observed due to dipole-dipole interaction. The emission intensity is enhanced upto 1.20 and 2.91 times on co-doping of Mg ²⁺ and Ca ²⁺ via induced crystal field due to charge imbalance. The emission intensity of the phosphor is found to enhance further on annealing the samples at 873 K. Under various excitation wavelengths, color tunability was seen from blue to bluish-white to red regions. The lifetime of the ⁵ D ₀ level of the Eu ³⁺ ion improves via doping of Mg ²⁺ /Ca ²⁺ ions and it increases appreciably on annealing. The temperature dependent photoluminescence study (TDPL) reveals a thermal quenching behavior of the sample with thermal stability ∼65% and activation energy ∼0.223 eV in the Eu ³⁺ /Ca ²⁺ co-doped ZnGa ₂ O ₄ phosphor sample.
Competing Interests: Authors declare that there is no conflict of interest in the present study.
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